Winglet

ABSTRACT

A winglet for attachment to a wing portion of an aircraft comprises a winglet tip and a winglet root opposite from the winglet tip. The winglet has an opening for receiving therethrough a connector for connecting the winglet to a wing portion in use. The winglet has a retainer internal of the winglet for use in retaining the connector relative to the winglet. The retainer has a hole that extends along an axis that passes through the opening for receiving therethrough a portion of the connector when the connector is located through the opening. The retainer comprising a body for reacting against a retention component with which the connector engages in use.

RELATED APPLICATIONS

The present application claims priority from Great Britain ApplicationNo. 1609142.3, filed May 24, 2016, the disclosure of which is herebyincorporated by reference herein in its entirety.

TECHNICAL FIELD

The present invention relates to aircraft wings, and in particular towinglets for attachment to wing portions of aircraft.

BACKGROUND

Aircraft wings may comprise devices at their wingtips to changeaerodynamic properties of the wings. For example, wing tip fences canact to control vortices at wingtips. Another example is winglets, whichtypically take the form of small wing-like structures at the end ofaircraft wings, and which are angled with respect to the rest of thewing. A winglet may be an upper portion of a wingtip device that istypically angled toward the upper (i.e. suction) surface of the wing, ora lower portion of a wingtip device that is typically angled toward thelower (pressure) surface of the wing. A winglet, for example an upperportion of a wingtip device, can improve the efficiency of an aircraftby improving the lift to drag ratio of a wing. Winglets can alsoincrease effective wingspan without substantially increasing the widthof an aircraft. For example, when a wing bends during flight, a lowerportion of a wingtip device at the end of the wing can become level soas to provide effective lift, and hence act as a quasi-span extensiondevice. Since the width of an aircraft is often restricted, for examplefor compatibility with airports, winglets that extend the effectivewingspan without extending the width of the plane can be of greatutility.

A drawback of some known fittings of winglets to wing portions, such asbutt strap fittings, is that interchange of parts so connected can takeconsiderable time and effort, for example, due to the considerablenumber of components that need to be removed and refitted. Interchangecan be particularly burdensome when complex wing geometries areinvolved, because such geometries can make achieving the requiredtolerances more difficult.

It would be advantageous for winglets to be easily and quickly attachedto, and detached from, wing portions. This would, for example, assistrapid exchange of a winglet for another winglet in the case of damagebeing sustained by the winglet in use. It would also be advantageous ifwinglets met interchangeability requirements, i.e. to be able to betaken “off the shelf” and be quickly and easily installed onto and/orremoved from a wing portion with minimum reworking of the winglet and/orwing portion.

SUMMARY

A first aspect of the present invention provides a winglet forattachment to a wing portion of an aircraft, the winglet comprising: awinglet tip; a winglet root opposite from the winglet tip and having anopening for receiving therethrough connector for connecting the wingletto a wing portion in use; and a retainer internal of the winglet and foruse in retaining the connector relative to the winglet in use, theretainer having a hole that extends along an axis that passes throughthe opening for receiving therethrough a portion of the connector whenthe connector is located through the opening, the retainer comprising abody for reacting against a retention component with which the connectorengages in use.

Optionally, the winglet root comprises a first thrust bearing forabutting against a second thrust bearing of the wing portion and fordefining a minimum distance between the winglet and the wing portion inuse.

Optionally, the winglet comprises a faring for forming a seal betweenthe winglet and the wing portion in use when the distance between thewinglet and the wing portion is at the minimum distance.

Optionally, the first thrust bearing is for receiving therethrough theconnector when the connector is located through the opening.

Optionally, the winglet comprises one or more spigots protruding fromthe winglet root for receipt into one or more corresponding recesses ofa said wing portion.

Optionally, the, or each, spigot is tapered.

Optionally, the winglet comprises upper and lower surfaces connectingthe winglet root to the winglet tip, and at least one of the upper andlower surfaces has an aperture to allow access to the retainer from theexterior of the winglet.

Optionally, the axis extends along a path at which a lift forceresulting from the winglet in use is greatest.

Optionally, the winglet is a lower portion of a wingtip device.

A second aspect of the invention provides a wing portion for anaircraft, the wing portion comprising: an upper surface and a lowersurface, at least one of the upper and lower surfaces defining a hole,the hole being for receiving a connector for connecting a winglet to thewing portion; and a fixing arrangement internal of the wing portion, thefixing arrangement being for fixing the connector in the hole.

Optionally, the hole is a blind hole.

Optionally, the fixing arrangement is for releasably fixing theconnector in the hole.

Optionally, the hole defines an axis that is perpendicular to the one ofthe upper and lower surfaces at a mouth of the hole.

Optionally, the lower surface defines the hole.

Optionally, the fixing arrangement comprises a threaded surface formating with a threaded surface of the connector.

Optionally, the threaded surface of the fixing arrangement is a femalescrew thread.

Optionally, the wing portion comprises one or more recesses forreceiving one or more corresponding spigots of the winglet in use.

Optionally, the, or each, recess extends along an axis that is parallelto an axis of the hole.

Optionally, the wing portion comprises the connector, and the connectoris received in the hole and is fixed in the hole by the fixingarrangement.

A third aspect of the invention provides a wing portion for an aircraft,the wing portion comprising an upper surface, a lower surface, and aconnector for connecting a winglet to the wing portion, the connectorprotruding from one of the upper and lower surfaces and having athreaded surface.

Optionally, the threaded surface is distal from the one of the upper andlower surfaces.

Optionally, the threaded surface is a male screw thread.

Optionally, the wing portion comprises one or more recesses forreceiving one or more corresponding spigots of the winglet in use.

Optionally, the, or each, recess extends along an axis that is parallelto an axis of the connector.

Optionally, the, or each, recess is tapered.

Optionally, the wing portion is or comprises an upper portion of awingtip device.

A fourth aspect of the invention provides a system, comprising: a wingportion for an aircraft, the wing portion having an upper surface and alower surface; a winglet according to the first aspect; and theconnector, wherein the connector protrudes from one of the upper andlower surfaces of the wing portion, or is for connection to the wingportion so as to protrude from the one of the upper and lower surfacesof the wing portion.

Optionally, the wing portion is according to the second aspect.

Optionally, the connector protrudes from the one of the upper and lowersurfaces of the wing portion, is located in the opening of the wingletroot, and is located in the hole of the retainer; and the retainercomprises the retention component, the retention component being engagedwith the connector and reacting against the body of the retainer toretain the connector in the winglet.

Optionally, the wing portion comprises the second thrust bearing, andsecond thrust bearing is abutting the first thrust bearing of thewinglet to define the minimum distance between the winglet and the wingportion.

Optionally, the system comprises a faring that forms a seal between thewinglet and the wing portion.

Optionally, the connector extends through the first thrust bearing.

Optionally, the retainer is adjustable so as to adjust the extent towhich the connector extends into the winglet.

Optionally, the connector comprises a first threaded surface, and theretention component comprises a second threaded surface for mating withthe first threaded surface.

Optionally, the first threaded surface is a male screw thread, and thesecond threaded surface is a female screw thread.

Optionally, the retainer comprises a positive retaining component tolimit movement of the retention component relative to the body of theretainer.

Optionally, the wing portion comprises the one or more correspondingrecesses, and wherein the one or more spigots are located in the one ormore recesses.

Optionally, the connector is received in the hole of the wing portionand is fixed in the hole of the wing portion by the fixing arrangement.

Optionally, the connector comprises a second threaded surface, and thefixing arrangement comprises a threaded surface for mating with thesecond threaded surface of the connector.

Optionally, the second threaded surface of the connector is a male screwthread, and the threaded surface of the fixing arrangement is a femalescrew thread.

Optionally, the connector is a cylindrical spar.

Optionally, the connector is removable from the wing portion and fromthe winglet.

Optionally, connector comprises a fusible portion.

A fifth aspect of the invention provides a method of attaching a wingletaccording to the first aspect to a wing portion of an aircraft, themethod comprising: providing a wing portion having an upper surface, alower surface, and a connector protruding from one of the upper andlower surfaces; inserting the connector through the opening of thewinglet root and into the hole of the retainer; and engaging a retentioncomponent with the connector so that the retention component reactsagainst the body of the retainer so as to retain the connector in thewinglet.

Optionally, the method comprises: inserting the connector into a hole inthe one of the upper and lower surfaces of the wing portion; and fixingthe connector in the hole in the one of the upper and lower surfaces ofthe wing portion.

Optionally, at least one of the winglet and the wing portion comprisesone or more spigots protruding therefrom, and at least one of the otherof the winglet and the wing portion comprises one or more correspondingrecess therein, and the method comprises: inserting the one or morespigots into the one or more corresponding recesses.

Optionally, the method comprises adjusting the retainer to adjust theextent to which the connector extends into the winglet.

A sixth aspect of the invention provides an aircraft comprising awinglet according to the first aspect, or comprising a wing portionaccording to the second or third aspects, or comprising a systemaccording to the fourth aspect.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of exampleonly, with reference to the accompanying drawings, in which:

FIG. 1 shows a schematic view of a winglet attached to a wing portionaccording to an embodiment of the invention;

FIG. 2 shows a schematic view of a winglet attached to a wing portionaccording to an embodiment of the invention;

FIGS. 3a to 3d show schematically a method of attaching a winglet to awing portion according to an embodiment of the invention; and

FIG. 4 shows a schematic view of an aircraft according to an embodimentof the invention.

DETAILED DESCRIPTION

Referring to FIGS. 1 and 2, in broad overview, a wing portion 102 (onlypartially illustrated in FIGS. 1 and 2 for clarity) of an aircraft (notitself shown in full in FIGS. 1 and 2) has connected thereto a winglet104. The wing portion 102 comprises a connector 106 protrudingtherefrom. The connector 106 extends into the winglet 104. The winglet104 comprises a retainer 108 internal of the winglet 104 for use inretaining the connector 106 relative to the winglet 104 in use. Theretainer 108 comprises a hole through which the connector 106 extends.The retainer 108 comprises a body 110 and a retention component 112 withwhich the connector 106 is engaged and which reacts against the body 110in use.

The wing portion 102 comprises an upper surface 116 (also known in theart as a suction surface 116) and lower surface 114 (also known in theart as a pressure surface 114), the lower surface 114 defining a hole(not visible in the figures) for receiving the connector 106. The upperand lower surfaces 116, 114 are “upper” and “lower” during normal use ofthe wing on the aircraft. The wing portion 102 comprises a fixingarrangement 122 internal of the wing portion 102 for fixing theconnector 106 in the hole (not visible). In this embodiment, theconnector 106 protrudes from the lower surface 114 of the wing portion102.

The wing portion 102 comprises an upper portion 150 at an end 170 of thewing distal to the fuselage of the aircraft (the end 170 extending intothe page in the sense of FIG. 1 and towards the left of the page in thesense of FIG. 2). For clarity, in FIGS. 1 and 2, the upper portion 150is only partially shown. Due to the continuous smooth curve along thespan of the wing portion 102, the wing portion 102 may itself beconsidered an upper portion 150 of a wingtip device. The winglet 104 isa lower portion 104 of the wingtip device. Together the upper portion150 and the lower portion 104 may form the wingtip device. It will beappreciated that although a wingtip device with an upper portion 150 andan attachable a lower portion 104 is illustrated, this need notnecessarily be the case in other embodiments. For example, in someembodiments the wing portion 102 may instead be or comprise a lowerportion of a wingtip device, and the winglet 104 may be an upper portionof the wingtip device for attaching to the wing portion 102.

The winglet 104 comprises a winglet tip 180 and a winglet root 182opposite from the winglet tip 180. When connected to the wing portion102, the winglet root 182 is closer to the wing portion 102 that thewinglet tip 180. The winglet tip 180 is that part of the winglet 104which is most distal from the wing portion 10:2 in use, whereas thewinglet root 182 is that portion most proximal the wing portion 102 inuse. The winglet root 182 has, or defines, an opening 184 for receivingtherethrough the connector 106 for connecting the winglet 104 to thewing portion 102. The hole of the retainer 108 extends along an axisthat passes through the opening 184, and the hole is for receivingtherethrough a portion of the connector 106 when the connector 106 islocated through the opening 184. The winglet 104 also has upper andlower surfaces that extend between the winglet root 182 and the winglettip 180.

The winglet 104 comprises a C-section spar 152 (also referred to hereinas C spar 152). The C spar 152 is internal of and fixedly connectedrelative to the winglet tip 180, winglet root 182 and upper and lowersurfaces of the winglet 104. The C spar 152 extends along the span ofthe winglet 104. A first section 154 of the C spar 152 is connected toan upper panel 156 of the winglet (for example using rivets or thelike), and a second section 158 of the C spar 152 is connected to alower panel (removed in the Figures for clarity) of the winglet 104 (forexample using rivets or the like), and a third section 160 of the C spar152 connects the first section 154 and the second section 158 of the Cspar 152 together. The first 154, second 158 and third 160 sectionsforma spar 152 with a “C”-shaped cross section.

The retainer 108 is located inside of the C spar 152 and comprises abody 110 (also referred to herein as a lower reaction fitting 110)through which the connector 106 extends. The lower reaction fitting 110is fixedly connected to each of the first 154, second 158, and third 160sections of the C spar (for example by welding or any other suitableconnection). The hole (not visible in the figures) of the retainer 108through which the connector 106 extends is a hole through the body 110of the retainer 108. At least a portion of an inner surface of the holeis a bearing face for the connector 106. For example, the connector 106is a cylindrical spar 106, and the lower reaction fitting 110 defines acylindrical hole through which the connector 106 extends. An innercylindrical surface (not visible in the figures) of the lower reactionfitting 110 acts as a bearing surface for the outer cylindrical surface106 of the connector 106 extending therethrough. The lower reactionfitting 110 can therefore effectively react against forces applied viathe connector 106, and vice versa. The cylindrical nature of theconnector 106 and the lower reaction fitting 110, and hence thecylindrical nature of the bearing surfaces thereof, provide direct loadpaths in all directions in the plane perpendicular to the longitudinalaxis of the connector 106.

The retainer 108 comprises a retention component 112 (e.g. a nut 112)with which the connector 106 is engaged and which reacts against thelower reaction fitting 110 to retain the connector 106 in the winglet104. For example, the connector 106 may comprise a first threadedsurface (not shown), and the retention component 112 may comprise asecond threaded surface (not shown) for mating with the first threadedsurface. For example, the first threaded surface may be a male screwthread and the second threaded surface may be a corresponding femalescrew thread. The lower reaction fitting 110 provides a surface (notvisible in the figures) perpendicular to the axis of the connector 106against which the nut 112 reacts, and hence which prevents the winglet104 from becoming detached from the wing portion 102. The first threadedsurface of the connector 106 is distal from the lower surface 114 of thewing portion 102.

The winglet 104 is arranged to provide access for manual adjustment ofthe retainer 108. Specifically, the lower surface (removed for clarityin the Figures) of the winglet 104 has an aperture to allow access tothe retainer 108 from the exterior of the winglet 104. An access panel(removed for clarity in the Figures) is movable to access the apertureand to reveal an access window 162 in the second section 158 of the Cspar 152. The access window 162 allows access to and manual adjustmentof the nut 112. For example, the nut 112 may be adjusted to adjust theextent to which the connector 106 extends into the winglet 104. Forexample, the access window 162 allows for the manual tightening of thenut 112 against lower reaction fitting 110, thereby to increase theextent to which the connector 106 extends into the winglet 104 until thewinglet 104 is tightened fast to the wing portion 102. Similarly, theaccess window 162 allows for the manual loosening of the nut 112 withrespect to the connector 106, thereby allowing the winglet 104 to bedetached from the wing portion 102. For example, the nut 112 may beloosened so as to be removed from the connector 106, thereby allowingthe connector 106 to be completely withdrawn from the lower reactionfitting 110 (and hence winglet 104), hence allowing the winglet 104 tobe removed from the wing portion 102. In other embodiments, the aperturemay be in the upper surface of the winglet 104.

The ability to fixedly connect the, winglet 104 to the wing portion 102by tightening a single nut 112, and indeed to disconnect and remove thewinglet 104 from the wing portion 102 by loosening a single nut,provides a particularly rapid and unlaborious way to attach and detach awinglet 104 to/from a wing portion 102. It is noted that since loadsparallel to the span of the winglet 104 are minimal in use, the loadsneeded to be reacted by the nut 112 are small.

The retainer 108 comprises a positive retaining component (not shown) tolimit movement of the retention component 112 (e.g. nut 112) relative tothe body 110 of the retainer 108. For example, a split pin may be usedto prevent the nut 112 from loosening with respect to the connector 106once the nut 112 has been tightened into place. This helps to ensurethat the attachment of the winglet 104 to the wing portion 102 issecure.

In some examples, the winglet 104 comprises a first thrust bearing (notshown), and the wing portion 102 comprises a second thrust bearing (notshown) that abuts against the first thrust hearing (not shown) when thewinglet 104 is attached to the wing portion 102. For example, when thenut 112 is tightened against the lower reaction fitting 110, and thewinglet 104 is thereby brought towards the wing portion 102, the firstthrust bearing of the winglet 104 and the second thrust bearing of thewing portion 102 will be brought towards each other until the firstthrust bearing abuts the second thrust bearing, such that the nut 112cannot be tightened further. The arrangement of the first and secondthrust bearings therefore define a minimum distance between the winglet104 and the wing portion 102. The first and second thrust bearings may,for example, be annular in shape, and the connector 106 may extendthrough the first and second thrust bearings. This may ensure thatforces parallel to the axis of the connector 106 may be symmetricallyreacted by the thrust bearings.

The winglet 104 comprises a faring 118 that forms a seal between thewinglet 104 and the wing portion 102, for example when the distancebetween the winglet 104 and the wing portion 102 is at the minimumdistance defined by the thrust bearings (not shown). The definition ofthe minimum distance by the thrust bearings may ensure that the fairing118 is not deformed on movement of the winglet 104 towards the wingportion 102. However, in some embodiments, the fairing may bedeformable. For example, the fairing may be resilient. This can helpprovide an improved seal.

An upper reaction fitting 164 is located in the C spar 152 at a locationalong the span of the winglet 104 proximal to the winglet, root 182. Theupper reaction fitting 164 is fixedly connected to the C spar 152 in thesame way as the lower reaction fitting 110. Similarly to the lowerreaction fitting 110, the upper reaction fitting 164 defines acylindrical hole through which the connector 106 extends, and provides abearing surface against which forces applied via the connector 106perpendicular to the axis of the connector 106 may be reacted, and viceversa. The upper reaction fitting 164 and the lower reaction fitting 110may together effectively react moments applied to the winglet 104 viathe connector 106, and vice versa.

The C spar 152 (and accordingly the connector 106 and the reactionfittings 110, 164) is located approximately centrally of the winglet104, i.e. approximately at the centre of the chord of the winglet 104.In this embodiment, the axis of the hole of the lower reaction fitting110 extends along a path at which the lift force resulting from thewinglet 104 in use is greatest. Accordingly, in use the connector 106extends along this path. The C spar 152, reaction fittings 110, 164, andconnector 106 may therefore effectively react lift forces caused by thewinglet 104 in use.

The winglet 104 comprises one or more spigots 120 a, 120 f protrudingfrom the winglet root 182, and the wing portion 102 comprises one ormore corresponding recess therein (not shown). The, or each, recessextends along an axis that is parallel to an axis of the hole in thewing portion 102 and parallel to the longitudinal axis of the connector106. The positions of the one or more spigots 120 a, 120 f andcorresponding one or more recesses (not shown) are axially offset withrespect to the connector 106. For example one spigot 120 f may belocated forward of the connector 106 (i.e. towards the leading edge 166of the winglet 104), and one spigot 102 a may be located aft of theconnector 106 (i.e. towards the trailing edge 168 of the winglet 104).The spigots 120 a, 120 f react against the corresponding recesses (notshown) (and vice versa) thereby to react moments of the winglet 104about the connector 106 in a plane perpendicular to the connector 106(i.e. torque loads). The upper reaction fitting 164, the lower reactingfitting 110, and the spigots 120 a, 120 f therefore provide direct loadpaths that provide reactions against movement of the winglet 104 withrespect to the wing portion 102 in all six degrees of freedom.

It will be appreciated that although two spigots 120 a, 120 f areillustrated protruding from the winglet 104, this need not necessarilybe the case. For example, in other embodiments only one spigot 120 f maybe used, or any number of spigots (e.g. 3, 4, 5. . . ) may be used.Further, one or more of the spigots may protrude instead from the wingportion 102, and there may be a corresponding one or more recesses inthe winglet 104 (such as in the winglet root 182) for receiving thespigot(s) of the wing portion 102. It will be appreciated that anycombination of spigots and recesses may be employed in either one of thewinglet 104 and wing portion 102.

At least one of the one or more spigots 120 a, 120 f may be tapered. Atleast one of the corresponding recesses (not shown) may be reciprocallytapered accordingly. This may assist the guiding of the one or morespigots 120 a, 120 f into the one or more corresponding recesses (notshown) when the winglet 104 and the wing portion 102 are broughttogether.

In this embodiment, the connector 106 extends partially into the wingportion 102, and the wing portion 102 comprises a fixing arrangement 122internal of the wing portion 102 that fixes the position of theconnector 106 with respect to the wing portion 102.

The fixing arrangement 122 and the connector 106 defines an axis(dot-dash line A in FIG. 2) that is perpendicular to a tangent (dot-dashline B in FIG. 2) to a lower surface 114 of the wing portion 102 at themouth of the hole (not shown) in the wing portion 102. Although notshown, it will be appreciated that in alternative arrangements, forexample if the winglet 104 is art upper portion of a wingtip device orotherwise, the hole may alternatively be in the upper surface 116 of thewing portion 102, and/or the connector 106 may alternatively define anaxis that is perpendicular to a tangent to the upper surface 116 of thewing portion 102 at the mouth of the hole.

The fixing arrangement 122 comprises an upper portion 172 that isfixedly connected to the upper surface 116 of the wing portion 120 andto a spar 176 of the wing portion 102, and a lower portion 124 (alsoreferred to herein is a main reaction fitting 124) that is fixedlyconnected to the lower surface 114 of the wing portion 102 and to thespar 176 of the wing portion 102. The upper portion 172 and the lowerportion 124 are in mechanical contact with each other so that loads canspread therebetween. The connector 106 extends through the hole (notvisible in the Figures) in the lower surface 114 of the wing portion102, and through a recess (not visible in the figures) of the mainreaction fitting 124 so as to be engaged with the upper portion 172 ofthe fixing arrangement 122. At least a portion of an inner surface ofthe recess of the main reaction fitting 124 is a bearing face for theconnector 106. For example, the connector 106 is a cylindrical spar 106,and the main reaction fitting 124 defines a cylindrical hole throughwhich the connector 106 extends. An inner cylindrical surface (notvisible in the figures) of the main reaction fitting 110 acts as abearing surface for the outer cylindrical surface 106 of the connector106 extending therethrough.

The fixing arrangement 122 releasably fixes the connector 106 to thewing portion 102. In this embodiment, the connector 106 comprises a malethreaded surface (not visible in the Figures), and the upper portion 172of the fixing arrangement 122 defines a bore (not visible in theFigures) with a corresponding female threaded surface for mating withthe male threaded surface of the connector 106. The connector 106 maytherefore be engaged with the bore of the upper portion 172 and rotatedabout its axis A-A thereby to tighten the connector 106 into the upperportion 172 of the fixing arrangement 122, and hence to fix theconnector with respect to the wing portion 102. The bore (not visible inthe Figures) has a closed end against which the connector 106 may abutwhen the connector 106 is fully tightened into the upper portion 172 ofthe fixing arrangement 122. It will be appreciated that in this case thehole in the lower surface 114 of the wing portion 102 is a blind hole.

If desired, the connector 106 may be unscrewed to release the connector106 from the fixing arrangement 122. It will therefore be appreciatedthat in this embodiment the connector 106 is removable from both thewing portion 102 and from the winglet 104. The ability to fixedlyconnect the winglet 104 to the wing portion 102 only by tightening theconnector 106 into the fixing arrangement 122 and the simple connectionof the winglet 104 to the connector 106 thereafter as described aboveprovides a particularly rapid and unlaborious way to attach (and indeeddetach) a winglet 104 to/from a wing portion 102. Moreover, removal ofthe connector 106 from the fixing arrangement 122 leaves only a smallhole (not visible in the figures) in the wing portion 102, which can becovered (if necessary) simply and quickly with an appropriate faring or“plug”, for example. Removal of the winglet 104 from the wing portion102 therefore necessitates little or no further alteration to wingportion 102 in order for the aircraft to fly without the winglet 104 ifdesired, and hence allows for particularly rapid attachment/detachmentof the winglet 104 to/from the wing portion 102.

Minimal components need to be accessed and/or removed in order toremove, exchange or install the winglet 104, which increases thereliability and longevity of the system. Access only to one side of thewinglet 104 is needed in order to attach/remove the winglet 104, hencefurther increasing the speed and simplicity of attachment/removal of thewing portion. No special tools are required to install and/or remove thewinglet 104. Moreover, since the attachment of the connector 106 to thewinglet 104 is internal of the winglet 104, winglets 104 of variousshapes and sizes can be interchangeably connected to the wing portion102 without any corresponding modification to the wing portion 102. Thatis, the system satisfies interchangeability (ICY) requirements. Theminimum distance between the winglet 104 and the wing portion 102defined by the abutting thrust bearings (not shown) allows the faring118 of the winglet 104 to provide predictable sealing of the winglet 104to the wing portion 102, and hence reduces the complexity of sealing ascompared to conventional designs.

The above described examples require a relatively few and simplecomponents as compared to conventional designs based on butt straps orthe like. This reduces the overall weight of the system as compared tosuch conventional designs.

In the above described examples, the resultant moment from the airpressure on the winglet 104 in use is reacted by the main reactionfitting 124 of the wing portion 102 and the upper reaction fitting 164of the winglet 104. The distance between the main reaction fitting 124and the upper reaction fitting 164 is relatively large (and independentof the thickness of the winglet 104), and hence the loads needed to bereacted by the main reaction fitting 124 and the upper reaction fitting164 for a given moment are relatively small. This is as compared to someconventional designs in which the moment is reacted at the upper andlower skins of the winglet, the distance between which is dependent onthe thickness of the winglet and can be relatively small, and hence theloads reacted relatively large and dependant on the thickness of thewinglet. The above described examples therefore reduce the reactionsrequired to be provided by the fittings in some cases by up to a third.Moreover, the above described examples react the loads from air pressureon the winglet 104 in the same plane as the skins (i.e. the upper andlower surfaces) of the winglet 104, which is more efficient than inconventional designs where this is not the case.

The connector 106 may comprise a fusible portion (not shown). That is, aportion of the connector 106 may be purposefully configured to fail orbreak at a predefined stress, for example sheer stress. This may beuseful to ensure that if the winglet 104 were to contact an externalobject with greater than a predetermined force, the winglet 104 detachesfrom the wing portion 102 before the force is able to damage the wingportion 102.

Referring to FIGS. 3a to 3d , an example method of attaching the winglet104 to the wing portion 102 is described.

In a first step as shown schematically in FIG. 3a , the connector 106 isinserted (arrow C) into the hole in the lower surface 114 of the wingportion 102 so as to engage with the fixing arrangement 122.

In a second step as shown schematically in FIG. 3b , connector 106 ismated (arrow D) with the fixing arrangement 122 to fix the connector 106with respect to the hole and the wing portion 102. In this embodiment,the male threaded surface of the connector 106 is engaged with thefemale threaded surface of the fixing arrangement 122 by rotating theconnector 106 in a clockwise fashion until the connector 106 abutsagainst a surface of the upper portion 172 of the fixing arrangement122. As a result of the first and second steps, the connector 106protrudes from the lower surface 114 of the wing portion 102. It will beunderstood that in other embodiments in which the hole in the wingportion 102 is through the upper surface 116 of the wing portion 102,the connector 106 would then protrude from the upper surface 116 of thewing portion 102.

In a third step as shown schematically in FIGS. 3c and 3d , the winglet104 is placed (arrows E) over the connector 106 so that the connector106 is inserted into the winglet 104 through the opening 184 of thewinglet root 182 and into the hole of the lower reaction fitting 110 ofthe retainer 108. At this stage, the spigots 120 a, 120 f of the winglet104 are inserted into the corresponding recesses (not shown in thefigures) in the wing portion 102.

In a fourth step as shown schematically in FIG. 3d , the retentioncomponent 112 (e.g. nut 112) is engaged with the connector 106 so thatthe retention component 112 reacts against the lower reaction fitting110 of the retainer 108 so as to retain the connector 106 in the winglet104. More specifically, in this embodiment a male threaded end 106 a ofthe connector 106 extends through the lower reaction fitting 110 (notvisible in FIG. 3d ), a female threaded nut 112 is manually engaged withthe male threaded end 106 a of the connector 106, and the nut 112 isrotated (arrow F) clockwise so as to tighten the nut 112 onto theconnector 106. The nut 112 is tightened (arrow F) until it abuts thelower reaction fitting 110 (not visible in FIG. 3). The nut 112 may thenbe further tightened so as to adjust the extent to which the connector106 extends into the winglet 104 until the winglet 104 is tightened fastto the wing portion 102. For example, the retainer 108 may be adjustedsuch that a first thrust bearing (not shown) of the winglet 104 and thesecond thrust bearing (not shown) of the wing portion 102 abut eachother to define a minimum distance between the wing portion 102 and thewinglet 104. At this stage, a positive retaining component (not shown),for example a split pin, may be inserted through a hole in the connector106 to help prevent loosening of the nut 112 with respect to theconnector 106.

It will be appreciated that the above steps can be performed in reverseso as to disconnect the winglet 104 from the wing portion 102. Briefly:After removing any positive retaining component (not shown) through theconnector 106, the nut 112 may be loosened (rotated anticlockwise) andremoved from the connector 106, and the connector 106 may be extractedfrom the winglet 104. The connector 106 may also be loosened (rotatedanticlockwise) and removed from the fixing arrangement 122 in the wingportion 102. The hole (not visible) in the lower surface 114 of the wingportion 102 may then be sealed by inserting an appropriately dimensionedfaring or plug.

FIG. 4 shows a schematic view of an example aircraft 400 comprising theabove described wing portion 102 and winglet 104.

Although the illustrated examples refer to the connector 106 extendinginto the wing portion 102 and being engaged into the fixing arrangement122, it will be appreciated that this need not necessarily be the case.In other examples, the wing portion 102 may comprise a connectorprotruding from an upper 116 or lower 114 surface of the wing portion102. In these examples, the connector 106 may have only one threadedsurface, for example a male thread, at an end 106 a of the connector 106distal from the wing portion 102.

Although in the above examples the connector 106 is a cylindrical sparwith a male threaded end 106 a received and secured into a femalethreaded nut 112, which nut reacts against the lower reaction fitting110, it will be appreciated that this need not necessarily be the case.For example, the nut may instead be a capped nut which is only open atone end. Indeed, it will be appreciated that there are many otherpossibilities for engaging a connector with a retention component thatreacts against a body of a retainer. In some embodiments, the connector1.06 need not be cylindrical, and at least a portion thereof may becuboidal or have any other shaped cross section. Accordingly, thereaction fittings 110, 172, 164 need not have cylindrical recesses, andmay be shaped accordingly to receive therethrough the connector 106 orportion thereof.

The above described examples are to be understood as illustrativeexamples only. Any feature described in relation to any one example maybe used alone, or in combination with other features described, and mayalso be used in combination with one or more features of any other ofthe examples, or any combination of any other of the examples.Furthermore, equivalents and modifications not described above may alsobe employed without departing from the scope of the invention, which isdefined in the accompanying claims.

The invention claimed is:
 1. A winglet for attachment to a wing portionof an aircraft, the winglet comprising: a winglet tip; a winglet rootopposite from the winglet tip and having an opening for receivingtherethrough a connector for connecting the winglet to a wing portion inuse; a retainer internal of the winglet and for use in retaining theconnector relative to the winglet in use, the retainer having a holethat extends along an axis that passes through the opening for receivingtherethrough a portion of the connector when the connector is locatedthrough the opening, the retainer comprising a body for reacting againsta retention component with which the connector engages in use; andwherein the retainer is located inside a spar.
 2. A winglet according toclaim 1, wherein the winglet root comprises a first thrust bearing forabutting against a second thrust bearing of the wing portion and fordefining a minimum distance between the winglet and the wing portion inuse.
 3. A winglet according to claim 2, comprising a faring for forminga seal between the winglet and the wing portion in use when the distancebetween the winglet and the wing portion is at the minimum distance, orwherein the first thrust bearing is for receiving therethrough theconnector when the connector is located through the opening.
 4. Awinglet according to claim 1, comprising one or more spigots protrudingfrom the winglet root for receipt into one or more correspondingrecesses of a said wing portion, optionally wherein the, or each, spigotis tapered.
 5. A winglet according to claim 1, further comprising upperand lower surfaces connecting the winglet root to the winglet tip,wherein at least one of the upper and lower surfaces of the winglet hasan aperture to allow access to the retainer from the exterior of thewinglet.
 6. An aircraft comprising a winglet according to claim
 1. 7. Awinglet according to claim 1, wherein the spar is a C spar.
 8. A wingletaccording to claim 7, wherein the C spar has an access window to allowaccess to the connector.
 9. A winglet according to claim 1, wherein theaxis extends along a path at which a lift force resulting from thewinglet in use is greatest.
 10. A winglet according to claim 1, whereinthe winglet is a lower portion of a wingtip device.
 11. A system,comprising: a wing portion for an aircraft, the wing portion having anupper surface and a lower surface; a winglet for attachment to a wingportion of an aircraft, the winglet comprising: a winglet tip; a wingletroot opposite from the winglet tip and having an opening for receivingtherethrough a connector for connecting the winglet to a wing portion inuse; and a retainer internal of the winglet and for use in retaining theconnector relative to the winglet in use, the retainer having a holethat extends along an axis that passes through the opening for receivingtherethrough a portion of the connector when the connector is locatedthrough the opening, the retainer comprising a body for reacting againsta retention component with which the connector engages in use; whereinthe retainer is located inside a spar; and, wherein the connectorprotrudes from one of the upper and lower surfaces of the wing portion,or is for connection to the wing portion so as to protrude from the oneof the upper and lower surfaces of the wing portion.
 12. A systemaccording to claim 11, wherein the connector protrudes from the one ofthe upper and lower surfaces of the wing portion, is located in theopening of the winglet root, and is located in the hole of the retainer;and wherein the retainer comprises the retention component, theretention component being engaged with the connector and reactingagainst the body of the retainer to retain the connector in the winglet,wherein the winglet root comprises a first thrust bearing for abuttingagainst a second thrust bearing of the wing portion and for defining aminimum distance between the winglet and the wing portion in use, andwherein the wing portion comprises the second thrust bearing, and thesecond thrust bearing is abutting the first thrust bearing of thewinglet to define the minimum distance between the winglet and the wingportion.
 13. A system according to claim 12, wherein the retainer isadjustable so as to adjust the extent to which the connector extendsinto the winglet, or wherein the retainer comprises a positive retainingcomponent to limit movement of the retention component relative to thebody of the retainer, or wherein the connector comprises a firstthreaded surface, and the retention component comprises a secondthreaded surface for mating with the first threaded surface, wherein thefirst threaded surface is a male screw thread, and the second threadedsurface is a female screw thread.
 14. A system according to claim 11,wherein the connector is a cylindrical spar, or wherein the connector isremovable from the wing portion and from the winglet, or wherein theconnector comprises a fusible portion.
 15. A method of attaching awinglet to a wing portion of an aircraft, the winglet comprising: awinglet tip; a winglet root opposite from the winglet tip and having anopening for receiving therethrough a connector for connecting thewinglet to a wing portion in use; and a retainer internal of the wingletand for use in retaining the connector relative to the winglet in use,the retainer having a hole that extends along an axis that passesthrough the opening for receiving therethrough a portion of theconnector when the connector is located through the opening, theretainer comprising a body for reacting against a retention componentwith which the connector engages in use, wherein the retainer is locatedinside a spar, the method comprising: providing a wing portion having anupper surface, a lower surface, and a connector protruding from one ofthe upper and lower surfaces; inserting the connector through theopening of the winglet root and into the hole of the retainer; andengaging the retention component with the connector so that theretention component reacts against the body of the retainer so as toretain the connector in the winglet.
 16. A method according to claim 15,further comprising inserting the connector into a hole in the one of theupper and lower surfaces of the wing portion; and fixing the connectorin the hole in the one of the upper and lower surfaces of the wingportion, or wherein at least one of the winglet and the wing portioncomprises one or more spigots protruding therefrom, and at least one ofthe other of the winglet and the wing portion comprises one or morecorresponding recess therein, and wherein the method comprises:inserting the one or more spigots into the one or more correspondingrecesses, or wherein the method comprises adjusting the retainer toadjust the extent to which the connector extends into the winglet.